In a single lens reflex camera, the image of the subject to be photographed is viewed through the lens on a focusing screen with the aid of a mirror disposed between the lens and the shutter. The mirror is angularly disposed such that it reflects the image received through the lens onto the screen before the picture is taken. When the shutter is activated, the mirror moves out of the path of the light to permit the light to pass onto the film.
In most reflex cameras, the mirrors are pivotably mounted to the camera body such that they swing out of the path between the lens and the shutter when the shutter is activated. The rotary motion requires a camera body with greater depth. Also, the number of times of mirror must pivot may create frequent servicing or failures.
One prior art solution is shown in U.S. Pat. No. 4,659,202 which issued to Sadre-Marandi et al on April 21, 1987. In that patent, the mirror and image focusing screen move together in a linear path to eliminate the problems associated with pivots. Also, the spacing between the lens and film may be smaller. In U.S. Pat. No. 4,659,202 a motor is used to cock the slide mechanism into the normal viewing position. Upon tripping, a pair of coil springs pull the mirror and image focusing screen out of the light path and the shutter then opens to allow exposure of the film. Springs are thus very crucial in that both springs must function perfectly in order to smoothly carry the support mechanism as desired.